expressing the uptake of transuranium nuclides from soil. in C.R. values are observed (ERDA, 1975; Schulz, 1977). Wide ranges A series of studies has been undertaken to ascertain for a given plant species and a given soil if the C.R. is constant. It is well known that C.R. will vary with addition of chelating agents (Adriano et aZ., 1971; Wallace, 1972a,b). The major purpose of this study was to determine how constant the C.R. would be with variation in the 2*/Am concentration uniformly mixed in soil. One set was made without chelate and one with the chelator DTPA (diethylenetriaminepentaacetate). MATERIALS AND METHODS The experiment was set up with Yolo loam soil (Typic Xerorthents, fine, silty, mixed, thermic) with activity of **lAm at 4,000, 10,000, 20,000, and 40,000 dpm/g soil. The activity was blended in for 1 hr with a batch mixer. There were four replications of 1,000 g each with and without DTPA, applied in solution at the rate of 100 ug/g soil. Nitrogen at the rate of 100 yg N per g soil as NH,NO3 was added to each pot. Soil moisture was maintained near -1/3 bar. Bush bean plants (Phaseolus vulgarts L. cv. Improved Tendergreen) were grown for 22 days, after which they were harvested. After standing for two months, these pots of soil were seeded to barley (Hordeum vulgare L. Atlas 57). Nitrogen was then applied as above. More DTPA was applied to the DTPA treatments (150 ug/g) one week after plants (20/pot) were seeded. One-third were harvested after another week. In 1] more days, another 1/3 were harvested and the other 1/3 after 13 more days. Then a second crop for all was harvested after 28 additional days. These were designated as harvests 1, 2, 3, and 4. AI1l were dried, weighed, and counted for 24 lam by gamma well counting. The counting time was usually for 1 hr. Only the data for barley are re- ported in this paper. In addition to C.R. values, "Y" uptake values were computed from the formula (C1/Co)* = uptake ratio (Wallace, 1977). RESULTS AND DISCUSSION The activity of @+!Am in plants was related to concentration in the soil The DTPA increased uptake manyfold and the effect was related (Table 1). to both concentration and time. The ratio of 24!Am for with DTPA without DTPA increased markedly with concentration except at the last 630